Artificial contoured spinal fusion implants made of a material other than bone

ABSTRACT

An interbody spinal implant made of a material other than bone adapted for placement across an intervertebral space formed across the height of a disc space between two adjacent vertebral bodies. The implant has a leading end that includes at least a portion of an arc of a circle from side to side, and sides that are at least in part straight or a trailing end having a radius of curvature of another circle from side to side.

RELATED APPLICATIONS

[0001] This application claims priority to provisional application No.60/281,187, filed Apr. 3, 2001, and provisional application No.60/281,124, filed Apr. 2, 2001, both of which are incorporated byreference herein.

FIELD OF THE INVENTION

[0002] The present invention relates generally to interbody spinalimplants preferably adapted for placement into an implantation spacecreated across the height of a disc space between two adjacent vertebralbodies for the purpose of correcting spinal disease at that interspace.The spinal implants are made of an implant material that is other thanbone and may or may not be resorbable. The implants are adapted suchthat fusion occurs at least in part through the implants.

DESCRIPTION OF THE RELATED ART

[0003] Implants for placement between adjacent vertebral bodies in thespine come in a variety of shapes and sizes and are made of a variety ofmaterials. Such implants for use in human spinal surgery includeimplants made of selected inert materials, such as titanium, that have astructure designed to promote fusion of the adjacent vertebral bodies byallowing bone to grow through the implant to thereby fuse the adjacentvertebral bodies.

[0004] The spinal disc that resides between adjacent vertebral bodiesmaintains the spacing between those vertebral bodies and, in a healthyspine, allows for relative motion between the vertebrae. At the time ofsurgery, for example in the instance where fusion is intended to occurbetween adjacent vertebral bodies of a patient's spine, the surgeontypically prepares an opening at the site of the intended fusion byremoving some or all of the disc material that exists between theadjacent vertebral bodies to be fused. Because the outermost layers ofbone of the vertebral end plate are relatively inert to new bone growth,the surgeon must work on the end plate to remove at least the outermostcell layers of bone to gain access to the blood-rich, vascular bonetissue within the vertebral body. In this manner, the vertebrae areprepared in a way that encourages new bone to grow into or through animplant that is placed between the vertebral bodies.

[0005] Present methods of forming this space between adjacent vertebralbodies generally include the use of one or more of the following: handheld biting and grasping instruments known as rongeurs; drills and drillguides; rotating burrs driven by a motor; osteotomes and chisels, and adouble wheel cutter or vertebral interspace preparation device. Inparticular, the double wheel cutter or vertebral interspace preparationdevice, as disclosed by Michelson in WO 99/63891, incorporated herein byreference, is adapted for linear insertion, i.e., insertion along asingle axis, and without the need to substantially move the device fromside to side within the disc space along a second axis. In such apreferred embodiment, the device has at its working end an abradingelement having a width generally corresponding to the width of theimplant to be implanted.

[0006] There is a desire to improve congruity at the interfaces of theimplant to the adjacent vertebral bodies, and to achieve stability ofthe implant. Therefore it is advantageous for the contour of theimplants to closely match the implantation space formed between and atleast in part into the adjacent vertebral bodies to allow a more uniformload transfer across the implant between the vertebral bodies.

[0007] As it is desirable to take advantage of all these benefits, thereexists a need for an improved interbody spinal fusion implant made of amaterial other than bone having a configuration that provides for animproved congruity of the implant to the vertebral bodies and improvedimplant stability.

SUMMARY OF THE INVENTION

[0008] In accordance with the purposes of the present invention, asembodied and broadly described herein, an artificial interbody spinalfusion implant made of a material other than bone is provided forinsertion at least in part into an implantation space formed across theheight of a disc space between adjacent vertebral bodies of a humanspine. The implant includes a leading end for insertion first into thedisc space and a trailing end opposite the leading end. The implant hasa length from the leading end to the trailing end. The leading end isconfigured in the shape of approximately one half of a circle from sideto side. The implant also includes opposed upper and lower portionsbetween the leading and trailing ends that are adapted to be placedwithin the disc space to contact and support the adjacent vertebralbodies. The upper and lower portions are non-arcuate along at least aportion of the length of the implant. The upper and lower portionsinclude at least one opening in communication with one another andadapted to hold bone growth promoting material for permitting for thegrowth of bone from vertebral body to vertebral body through theimplant. The implant also includes opposite sides between the upperportion and lower portion, and between the leading and trailing ends. Atleast one of the opposite sides is at least in part straight along atleast a portion of the length of the implant.

[0009] In accordance with the purposes of the present invention, asembodied and broadly described herein, an interbody spinal fusionimplant made of a material other than bone is provided for insertion atleast in part into an implantation space formed across the height of adisc space between adjacent vertebral bodies of a human spine. Theimplant includes a leading end for insertion first into the disc spaceand a trailing end opposite the leading end. The implant has a lengthfrom the leading end to the trailing end. The leading end is configuredfrom side to side in the shape of approximately one half of a firstcircle. The trailing end has a radius of curvature of a second circlefrom side to side. The second circle has a radius greater than theradius of the first circle. The implant also includes opposed upper andlower portions between the leading and trailing ends that are adapted tobe placed within the disc space to contact and support the adjacentvertebral bodies. The upper and lower portions include at least oneopening in communication with one another and adapted to hold bonegrowth promoting material for permitting for the growth of bone fromvertebral body to vertebral body through the implant. The implant has amaximum width that is greater than one-half of the width of the adjacentvertebral bodies into which the implant is adapted to be inserted.

[0010] Additional objects and advantages of the invention will be setforth in part in the description which follows, and in part will beobvious from the description, or may be learned by practice of theinvention. The objects and advantages of the invention will be realizedand attained by means of the elements and combinations particularlypointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a top plan view of a vertebral body in the lumbar spinewith an implantation space formed to receive a spinal implant having aradius of curvature at the leading end that is less than the radius ofcurvature of the trailing end of the anterior aspect of the vertebralbody between the sides of the implantation space.

[0012]FIG. 2 is a side elevation view of two adjacent vertebral bodiesin the lumbar spine with the implantation space of FIG. 1 formed acrossthe height of the spinal disc and into the adjacent vertebral bodies.

[0013]FIG. 3 is a side perspective view of the implantation space ofFIG. 1.

[0014]FIG. 4 is a top plan view of a vertebral body in the cervicalspine with an implantation space formed to receive a spinal implanthaving a radius of curvature at the leading end that is less than theradius of curvature of the trailing end of the anterior aspect of thevertebral body.

[0015]FIG. 5 is a side elevation view of two adjacent vertebral bodiesin the cervical spine with the implantation space of FIG. 4 formedacross the height of the spinal disc and into the adjacent vertebralbodies.

[0016]FIG. 6 is a side perspective view of the implantation space ofFIG. 4.

[0017]FIG. 7 is a top plan view of a vertebral body in the lumbar spineand a preferred embodiment of an implant in accordance with the presentinvention installed into the implantation space of FIG. 1.

[0018]FIG. 8 is a side elevation view of two adjacent vertebral bodieswith the implant of FIG. 7 installed into the implantation space of FIG.1 formed across the height of the spinal disc and into the adjacentvertebral bodies.

[0019]FIG. 9 is a top plan view of the implant of FIG. 7.

[0020]FIG. 10 is a side elevation view of the implant of FIG. 7.

[0021]FIG. 11 is a leading end view of the implant of FIG. 7.

[0022]FIG. 12 is a trailing end view of the implant of FIG. 7.

[0023]FIG. 13 is a top plan view of another preferred embodiment of animplant in accordance with the present invention for use in theimplantation space of FIG. 4.

[0024]FIG. 14 is a rear perspective view of another preferred embodimentof an implant in accordance with another preferred embodiment of thepresent invention having two members that are preferably mirror imagesof one another.

[0025]FIG. 15 is a top plan view of one of the members of the implant ofFIG. 14.

[0026]FIG. 16 is an interior side elevation view of one of the membersof the implant of FIG. 14.

[0027]FIG. 17 is an exterior side elevation view of one of the membersof the implant of FIG. 14.

[0028]FIG. 18 is a leading end view of one of the members of the implantof FIG. 14.

[0029]FIG. 19 is a trailing end view of one of the members of theimplant of FIG. 14.

[0030]FIG. 20 is a top plan view of another preferred embodiment of animplant in accordance with the present invention with bone engagingscrews.

[0031]FIG. 21 is a side elevation view of the implant of FIG. 20.

[0032]FIG. 22 is a leading end view of the implant of FIG. 20.

[0033]FIG. 23 is a trailing end view of the implant of FIG. 20 with thebone engaging screws and lock installed.

[0034]FIG. 24 is a trailing end view of the implant of FIG. 23 withoutthe bone engaging screws and lock installed.

[0035]FIG. 25 is a partial cross sectional side view of a preferredembodiment of a bone screw lock in accordance with the present inventionfor use with the implant of FIG. 20.

[0036]FIG. 26 is a cross sectional side view of another preferredembodiment of a bone screw lock in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0037] The following description is intended to be representative onlyand not limiting and many variations can be anticipated according tothese teachings, which are included within the scope of this inventiveteaching. Reference will now be made in detail to the preferredembodiments of this invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

[0038] FIGS. 1-3 show an implantation space 50 formed across the heightof the space occupied by a spinal disc D and into vertebral bodies V inthe lumbar spine. Implantation space 50 is preferably formed with theapparatus and method disclosed by Michelson in U.S. Pat. No. 6,083,228,and WO 99/63891, the disclosures of which are both incorporated hereinby reference. The instruments and method are not the subject matter ofthis application. It is understood that the preparation of theimplantation space shown therein are a preferred instrument and methodof preparing the implantation spaces and that any method andinstrumentation suitable for the purpose may be utilized to prepare thedesired implantation space adapted to receive the implants of thepresent invention.

[0039] Implantation space 50 is preferably formed in the endplate regionER in the subchondral bone of the vertebral body V. Implantation space50 preferably is formed to have a leading edge 52 with a shape from sideto side of approximately one-half of a first circle A. The trailingportion 54 of implantation space 50 preferably includes at least aportion of the anterior aspect of the vertebral body having a radius ofcurvature of a second circle B from side to side. Preferably the radiusof circle A is less than the radius of circle B. Implantation space 50may further include side edges 56, 58. Side edges 56, 58 preferablyinclude at least a straight portion, may be parallel to one anotheralong lines P and form a curved transition with leading edge 52.

[0040] FIGS. 4-6 show an implantation space 60 formed across the heightof the space occupied by a spinal disc D and into vertebral bodies V inthe cervical spine. Implantation space 60 preferably is formed to have aleading edge 62 with a shape from side to side of approximately one halfof a first circle A. The trailing portion of implantation space 60preferably includes at least a portion of the anterior aspect of thevertebral body having a radius of curvature of a second circle C fromside to side. Preferably the radius of circle A is less than the radiusof circle C. Implantation space 60, however, preferably does not havestraight side edges like implantation space 50 because the anterior toposterior depth of cervical vertebral bodies is less than the anteriorto posterior depth of lumbar vertebral bodies. Thus, the radius ofcircle C is smaller in the cervical spine than the radius of circle B inthe lumbar spine.

[0041] FIGS. 7-12 show an implant 100 in accordance with a preferredembodiment of the present invention. Implant 100 has a leading end 102for insertion first into the disc space between two adjacent vertebralbodies and a trailing end 104 opposite leading end 102, and oppositesides 110, 112 therebetween. Leading end 102 is preferably configured tomatch the contour of leading edge 52 of implantation space 50 andtrailing end 104 is preferably configured to conform to the contour ofthe anterior aspect of the vertebral body at trailing portion 54 ofimplantation space 50. Sides 110, 112 are generally planar andpreferably correspond to the configuration of side edges 56, 58 ofimplantation space 50.

[0042] In a preferred embodiment of the present invention, leading end102, trailing end 104, and opposite sides 110, 112 may have variousconfigurations. Leading end 102 is preferably is in the shape ofapproximately half a first circle from side to side. Where theimplantation space is prepared into the vertebral bodies to have a lipor ridge that is at least in part curved, leading end 102 may be adaptedto abut at least that portion of the implantation space.

[0043] One or both of sides 110, 112 may also be formed to be at leastin part oriented generally parallel to the mid-longitudinal axis ofimplant 100 and/or to each other. One or both of sides 110, 112 mayinclude at least one opening 119 to permit for the growth of bonetherethrough and into implant 100, though the invention is not solimited. Further, leading end 102 may be tapered to facilitate insertionof implant 100 between the two adjacent vertebral bodies.

[0044] Trailing end 104 preferably forms an arc of a second circle fromside to side having a radius greater than the radius of the first circleassociated with leading end 102. Preferably, at least a portion oftrailing end 104 is adapted to conform to at least a portion of theperipheral contour of the anterior aspect of the vertebral bodiesadjacent the disc space into which the implant is adapted to beinserted, though the invention is not so limited.

[0045]FIG. 12 shows that implant 100 preferably has a driver opening 116at trailing end 104 for cooperatively engaging an instrument forinstalling implant 100 into the implantation space. Driver opening 116is preferably configured for threaded engagement with an insertioninstrument.

[0046]FIGS. 8, 10, and 11 show at least a portion of upper and lowersurfaces 106, 108 in an angular relationship to each other from trailingend 104 to leading end 102 for allowing for angulation of the adjacentvertebral bodies relative to each other. Preferably, upper and lowersurfaces 106, 108 are non-arcuate in a direction along themid-longitudinal axis of implant 100. Implant 100 preferably has amaximum height that is less than the maximum width of the implant.

[0047] As shown in FIG. 9, upper and lower surfaces 106, 108 preferablyhave at least one opening 114 passing therethrough between leading andtrailing ends 102, 104, respectively, and opposite sides 110, 112.Openings 114 are preferably adapted to hold bone growth promotingmaterial to permit for the growth of bone from vertebral body tovertebral body through openings 114 and through implant 100. Upper andlower surfaces 106, 108 may also be porous and may include a bone ingrowth surface.

[0048] As shown in FIG. 9, the implants described herein may include abone-engaging surface 118 such as knurling for example. Bone engagingsurface 118 is configured to engage the bone of the adjacent vertebralbodies to maintain implant 100 within the adjacent vertebral bodiesafter implantation. Other preferred embodiments of bone-engagingsurfaces may include the surfaces of the implant being roughened,ratcheted, splined, or may include at least one protrusion to penetrablyengage the bone of the vertebral bodies. By way of example only, theimplants of the present invention may include the surface configurationtaught by Michelson in U.S. patent application Ser. No. 09/457,228,entitled “Spinal Implant Surface Configuration,” the disclosure of whichis incorporated by reference herein.

[0049] Bone for use as the base material used to form the implant of thepreferred embodiment is specifically excluded for the purpose of thisapplication. Where the implants are for spinal fusion, it is appreciatedthat they may be adapted to receive fusion promoting substances and/ormaterials within them such as, but not limited to cancellous bone, bonederived products, or others. In a preferred embodiment, the material ofthe implant is formed of material other than bone, such as metalincluding, but not limited to, titanium and its alloys, ASTM material,cobalt chrome, or tantalum, ceramic, various surgical grade plastics,plastic composites, carbon fiber composites, coral, and can includeartificial materials which are at least in part bioresorbable.

[0050] Upper and lower surfaces that are angled relative to each other,when subsequently implanted into the spine, position the adjacentvertebral bodies in angular relationship to each other to restore thenatural curvature of the spine, such as lordosis for example.

[0051] The implant may have a selected shape suitable for the intendedpurpose. For example only, the leading end may be in the shape ofapproximately one half of a circle from side to side. The sides may beat least in part straight. The trailing end may have any desired shapesuitable for the intended purpose and may preferably conform to theanatomical contour of the adjacent vertebral bodies between which theimplant is adapted to be inserted.

[0052] Implant 100 preferably has a length greater than one-half thedepth of the vertebral bodies adjacent the disc space into which theimplant is adapted to be inserted as measured between the anterior andposterior aspects of the vertebral bodies. Implant 100 also preferablyhas a maximum width that is greater than one-half the width of theadjacent vertebral bodies into which the implant is adapted to beinserted.

[0053]FIG. 13 shows another preferred embodiment of the presentinvention for use in the cervical spine generally referred to by thenumeral 200. Implant 200 is preferably configured to conform to theshape of implantation space 60 formed in the endplates of adjacentcervical vertebral bodies with instrumentation and methods similar tothose used in association with the lumbar spine but modified for use inthe cervical spine. Implant 200 may, for example, have a leading end 202formed to have a shape of approximately one-half a first circle fromside to side. Trailing end 204 preferably may be formed as an arc of asecond circle from side to side that intersects the curvature of leadingend 202 from side to side. The radius of the second circle associatedwith trailing end 204 is preferably greater that the radius of the firstcircle associated with leading end 202.

[0054] FIGS. 14-19 show an implant 300 in accordance with anotherpreferred embodiment of the present invention adapted for use from theanterior approach to the spine. FIG. 14 shows a rear perspective view ofimplant 300. Implant 300 includes at least two members 300′, 300″ thatare adapted to be placed side by side with one another. Member 300′ ispreferably, but need not be a mirror image of member 300″. Thedescription of member 300′ is equally applicable to member 300″. Member300′ has a leading portion 302′ for insertion first into the disc spacebetween two adjacent vertebral bodies and a trailing portion 304′opposite leading portion 302′. Member 300′ has a top 306′, a bottom308′, an interior side 310′, and an exterior facing side 312′ oppositeinterior facing side 310′. As used herein, the phrase “interior side”describes the side of the member adapted to be orientated toward theinterior side of another member when a pair of members are inserted sideby side into the disc space.

[0055] Leading portions 302′, 302″ of each member 300′, 300″,respectively, form leading end 302 of implant 300 when the members areplaced side by side to one another. Leading end 302 of implant 300 ispreferably configured in the shape of one-half a first circle from sideto side. Trailing end 304, composed of trailing portions 304′, 304″ whenmembers 300′, 300″ are placed side by side to one another, may, but neednot be formed as an arc of a second circle side to side having a radiusgreater than a radius of the first circle associated with leading end302 of implant 300.

[0056] Member 300′ is placed side by side with member 300″ so that aportion of interior side 310′ of each member are adjacent one another.Top 306′ and bottom 308′ preferably have at least one opening 314′passing therethrough between leading and trailing portions 302′, 304′,respectively, and sides 310′, 312′. Openings 314′ are adapted to holdbone growth promoting material to permit for the growth of bone fromvertebral body to vertebral body through openings 314. Interior side310′ may also include at least one opening 314′ passing therethroughconfigured to permit bone growth between and into adjacent members 300′,300″. Member 300′ preferably has a maximum width W that is less thanapproximately one-half the width of the adjacent vertebral bodies intowhich the member is adapted to be inserted. Also, the combined width ofboth members 300′, 300″ is preferably greater than one-half the width ofthe adjacent vertebral bodies into which the members are adapted to beinserted.

[0057] Members 300′, 300″ provide the added advantage in that eachmember can be inserted through a smaller space than a single largerimplant, to achieve the same effect as the larger implant.

[0058] In another preferred embodiment the implant of the presentinvention may be adapted for use from an anterior approach to the spineand have a maximum width between its sides that is less than one-half ofthe width of the adjacent vertebral bodies into which the implant isadapted to be inserted. The implant may have a leading end that isshaped as approximately one-half a first circle. The implant may alsohave a trailing end that forms an arc of a second circle having a radiusthat is substantially greater than the radius of the first circleassociated with the leading end.

[0059] In another preferred embodiment, the implant of the presentinvention may be adapted for use from an anterior approach to the spineand have preferably both the leading and trailing ends in the shape ofapproximately one half of a circle side to side.

[0060] In another preferred embodiment the implant of the presentinvention may be adapted for use from a posterior approach to the spineand have a trailing end that is preferably at least in part straightfrom side to side.

[0061] FIGS. 20-26 show an implant 400 in accordance with anotherembodiment of the present invention. Implant 400 is similar to implant100 and has a leading end 402 in the shape of approximately one-half afirst circle A and a trailing end 404 formed as an arc of a secondcircle C. Implant 400 preferably includes straight portions 411, 413along at least a portion of sides 410, 412, respectively, that arepreferably parallel to each other along lines P. Implant 400 alsopreferably includes a curved transition from each straight portion 411,413 of sides 410, 412, respectively, to trailing end 404 to form roundedportions 415, 417, respectively. Rounded portion 415, 417 may be an arcof a third circle E that preferably has a radius less than the radii ofcircle A associated with leading end 402 and/or circle C associated withtrailing end 404.

[0062] In a preferred embodiment, implant 400 may be adapted to receivethrough bone screw receiving holes 420 at trailing end 404 at least apair of opposed appropriately sized bone screws 422. Bone engagingscrews 422 may be aligned or offset from each other. At least one screw422 engages each of the vertebral bodies adjacent a disc space to befused and into which implant 400 is implanted. A purpose of the bonescrews is to rigidly secure the implant within the vertebral segment. Afurther purpose is to pull each of the adjacent vertebral bodies towardthe implant and towards each other. Trailing end 404 of implant 400preferably includes a recess 424 having bone screw receiving holes 420therein and an opening 426 configured to cooperatively receive a lockingcap 428 adapted to lock at least one bone screw 422 to implant 400.

[0063] As shown in FIG. 25, implant 400 is preferably adapted to receivea lock 428 at trailing end 404 for securing bone engaging screws 422therein and preventing the screws from backing out. Locking cap 428 hasa top 430, a stem 432, and a tool engagement area 434. In use, lockingcap cooperatively engages trailing end 404 of implant 400 at opening 426to lock at least one bone screw to implant 400. If desired, locking cap428 may include a thread on stem 432 to allow locking cap 428 torotationally engage implant 400.

[0064]FIG. 26 shows another preferred embodiment of a locking cap,generally referred to by the numeral 436. Locking cap 436 includes a top438 having a thread 440 at its outer perimeter that is adapted tocooperatively engage a corresponding threaded recess in the implant.

[0065] The implant, bone screws, and/or locks can be made of abioresorbable material, including but not limited to plastics andcomposite plastics. Suitable plastics may include those comprisinglactides, galactides, glycolide, capronlactone, trimethylene carbonate,or dioxanone in various polymers, and/or combinations thereof.

[0066] By way of example only and not limitation, for use in the lumbarspine, the implants of the present invention may have a depth ofapproximately, 28-36 mm, a width of approximately, 30-38 mm, and aheight (max) of approximately 8-20 mm. The radius of curvature of theleading end may be approximately 15-19 mm and the radius of curvature ofthe trailing end may be approximately 20-30 mm.

[0067] In any of the embodiments of the present invention, the implantmay include, be made of, treated, coated, filled, used in combinationwith, or have a hollow or opening for containing artificial or naturallyoccurring materials and/or substances suitable for implantation in thehuman spine. These materials and/or substances include any source ofosteogenesis, bone growth promoting materials, bone, bone derivedsubstances or products, demineralized bone matrix, mineralizingproteins, ossifying proteins, bone morphogenetic proteins,hydroxyapatite, genes coding for the production of bone, and boneincluding, but not limited to, cortical bone. The implant can include atleast in part of materials that are bioabsorbable and/or resorbable inthe body such as bone and/or bone growth promoting materials. Theimplant of the present invention can be formed of a porous material orcan be formed of a material that intrinsically participates in thegrowth of bone from one of adjacent vertebral bodies to the other ofadjacent vertebral bodies. Where such implants are for posteriorimplantation, the trailing ends of such implants may be treated with,coated with, or used in combination with chemical substances to inhibitscar tissue formation in the spinal canal. The implant of the presentinvention may be modified, or used in combination with materials to makeit antibacterial, such as, but not limited to, electroplating or plasmaspraying with silver ions or other substance. At least a portion of theimplant may be treated to promote bone in growth between the implant andthe adjacent vertebral bodies. The implant of the present invention maybe used in combination with a spinal fixation implant such as anyobject, regardless of material, that can be inserted into any portion ofthe spine, such as but not limited to interbody spinal implants,structural bone grafts, mesh, cages, spacers, staples, bone screws,plates, rods, tethers of synthetic cords or wires, or other spinalfixation hardware

[0068] While the shapes of the various aspects of the implant have beendescribed precisely, the scope of the present invention is not solimited and it is readily anticipated that the contours may beinterrupted by minor irregularities such as for example only for thepurpose of engaging the bone, encouraging the in growth or throughgrowth of bone.

[0069] While specific innovative features were presented in reference tospecific examples, they are just examples, and it should be understoodthat various combinations of these innovative features beyond thosespecifically shown are taught such that they may now be easilyalternatively combined and are hereby anticipated and claimed.

What is claimed is:
 1. An artificial interbody spinal implant forinsertion at least in part into an implantation space formed across theheight of a disc space between adjacent vertebral bodies of a humanspine, the vertebral bodies having an anterior aspect and a posterioraspect and a depth therebetween, said implant comprising: a leading endfor insertion first into the disc space and a trailing end opposite saidleading end, said implant having a length from said leading end to saidtrailing end; opposed upper and lower portions between said leading andtrailing ends adapted to be placed at least in part within and acrossthe height of the disc space to contact and support the adjacentvertebral bodies, said upper and lower portions defining a height ofsaid implant, said upper and lower portions being non-arcuate along atleast a portion of the length of said implant; and opposite sidesbetween said upper portion and said lower portion, and between saidleading and trailing ends, said opposite sides defining a width of saidimplant, at least one of said opposite sides being at least in partstraight along at least a portion of the length of said implant, saidleading end configured in the shape of approximately one half of acircle from one of said opposite sides to another one of said oppositesides, the circle having a diameter generally equal to the width of saidimplant, the width of said implant being greater than the height of saidimplant; said implant being manufactured from a material other thanbone, said upper and lower portions of said implant including at leastone opening in communication with one another and adapted to hold bonegrowth promoting material for permitting for the growth of bone fromvertebral body to vertebral body through said implant.
 2. The implant ofclaim 1, wherein said implant has a maximum width between said oppositesides that is greater than one-half of the width of the adjacentvertebral bodies into which said implant is adapted to be inserted. 3.The implant of claim 1, wherein said implant has a maximum width betweensaid opposite sides that is less than one-half of the width of theadjacent vertebral bodies into which said implant is adapted to beinserted.
 4. The implant of claim 3, wherein said implant is adapted tobe inserted side by side a second of said implant into the disc spacebetween the adjacent vertebral bodies.
 5. The implant of claim 1,wherein at least a portion of said leading end has a reduced height tofacilitate insertion of said implant between the two adjacent vertebralbodies.
 6. The implant of claim 1, wherein said trailing end is adaptedto conform from side to side to at least a portion of the peripheralcontour of at least one of the anterior and posterior aspects of thevertebral bodies adjacent a disc space into which said implant isinserted.
 7. The implant of claim 1, wherein said trailing end has aradius of curvature of a second circle from side to side.
 8. The implantof claim 7, wherein the radius of curvature said trailing end is greaterthan the radius of curvature of the leading end of said implant.
 9. Theimplant of claim 1, wherein said at least one opening is between saidopposite sides of said implant.
 10. The implant of claim 1, wherein saidat least one opening intersects at least one of said opposite sides. 11.The implant of claim 1, wherein said at least one opening is betweensaid leading and trailing ends of said implant.
 12. The implant of claim1, wherein said implant has a mid-longitudinal axis along the length, atleast one of said opposite sides being at least in part orientedgenerally parallel to the mid-longitudinal axis of said implant.
 13. Theimplant of claim 1, wherein said opposite sides are at least in partgenerally parallel one another.
 14. The implant of claim 1, wherein atleast a portion of said upper and lower surfaces are in an angularrelationship to each other from trailing end to leading end for allowingangulation of the adjacent vertebral bodies relative to each other. 15.The implant of claim 1, wherein said implant has a maximum length lessthan and approximating the posterior to anterior depth of the vertebralbodies.
 16. The implant of claim 1, further comprising a bone engagingsurface formed on the exterior of at least said upper and lower portionsfor engaging the adjacent vertebral bodies, said bone engaging surfaceincluding at least one of a protrusion, a ratchet, a spike, a spline,surface roughenings, and knurling.
 17. The implant of claim 1, whereinsaid implant includes at least two members, each member having a leadingportion, a trailing portion, a top, a bottom, and at least one side,each member being adapted to be placed side by side with another of saidmembers, said leading portion of said members forming said leading endof said implant when placed side by side.
 18. The implant of claim 17,wherein said implant includes two of said members, each member being amirror image of the other.
 19. The implant of claim 17, wherein eachmember includes at least a portion of said at least one opening.
 20. Theimplant of claim 1, in combination with a bone growth promotingmaterial.
 21. The implant of claim 20, wherein said bone growthpromoting material is selected from one of bone, bone derived products,demineralized bone matrix, mineralizing proteins, ossifying proteins,bone morphogenetic protein, hydroxyapatite, and genes coding for theproduction of bone.
 22. The implant of claim 1, wherein said implant istreated with a bone growth promoting substance.
 23. The implant of claim1, wherein said implant is at least in part resorbable.
 24. The implantof claim 1, in combination with a chemical substance adapted to inhibitscar formation.
 25. The implant of claim 1, in combination with anantimicrobial material.
 26. The implant of claim 1, wherein at least aportion of said implant is treated to promote bone in growth betweensaid implant and said adjacent vertebral bodies.
 27. The implant ofclaim 1, in combination with at least one spinal fixation implant. 28.The implant of claim 1, wherein said trailing end is adapted to receiveat least one bone screw adapted to engage at least one vertebral bodywhen inserted through said implant.
 29. The implant of claim 28, furthercomprising a lock for locking at least one bone screw to said implant.30. An artificial interbody spinal implant for insertion at least inpart into an implantation space formed across the height of a disc spacebetween adjacent vertebral bodies of a human spine, the vertebral bodieshaving an anterior aspect and a posterior aspect and a depththerebetween, said implant comprising: a leading end for insertion firstinto the disc space and a trailing end opposite said leading end, saidimplant having a length from said leading end to said trailing end;opposed upper and lower portions between said leading and trailing endsadapted to be placed at least in part within and across the height ofthe disc space to contact and support the adjacent vertebral bodies;said implant having a maximum width that is greater than one-half of thewidth of the adjacent vertebral bodies into which said implant isadapted to be inserted, said leading end configured in the shape ofapproximately one half of a first circle along the width of saidimplant, said trailing end having a radius of curvature of a secondcircle along the width of said implant, the second circle having aradius greater than the radius of the first circle; and said implantbeing manufactured from a material other than bone, said upper and lowerportions of said implant including at least one opening in communicationwith one another and adapted to hold bone growth promoting material forpermitting for the growth of bone from vertebral body to vertebral bodythrough said implant.
 31. The implant of claim 30, wherein said leadingend and said trailing end of said implant intersect at diametricallyopposite points of said implant.
 32. The implant of claim 30, whereinsaid width of said implant is approximately equal to the diameter of thefirst circle.
 33. The implant of claim 30, wherein said implant has aheight from said upper portion to said lower portion, the height of saidimplant being less than the maximum width of said implant.
 34. Theimplant of claim 30, wherein at least a portion of said leading end hasa reduced height to facilitate insertion of said implant between the twoadjacent vertebral bodies.
 35. The implant of claim 30, wherein saidtrailing end is adapted to conform from side to side to at least aportion of the peripheral contour of the anterior aspect of thevertebral bodies adjacent a disc space into which said implant isinserted.
 36. The implant of claim 30, wherein said implant has aperimeter, said at least one opening being within said perimeter of saidimplant.
 37. The implant of claim 30, wherein said implant has aperimeter, said at least one opening intersecting at least a portion ofsaid perimeter of said implant.
 38. The implant of claim 30, whereinsaid at least one opening is between said leading and trailing ends ofsaid implant.
 39. The implant of claim 30, further comprising oppositesides between said leading end and said trailing end.
 40. The implant ofclaim 39, wherein at least one of said opposite sides is at least inpart straight along at least a portion of the length of said implant.41. The implant of claim 39, wherein said implant has a mid-longitudinalaxis along the length, at least one of said opposite sides being atleast in part oriented generally parallel to the mid-longitudinal axisof said implant.
 42. The implant of claim 39, wherein said oppositesides are at least in part generally parallel one another.
 43. Theimplant of claim 30, wherein at least a portion of said upper and lowersurfaces are in an angular relationship to each other from trailing endto leading end for allowing angulation of the adjacent vertebral bodiesrelative to each other.
 44. The implant of claim 30, wherein saidimplant has a maximum length less than and approximating the posteriorto anterior depth of the vertebral bodies.
 45. The implant of claim 30,further comprising a bone engaging surface formed on the exterior of atleast said upper and lower portions for engaging the adjacent vertebralbodies, said bone engaging surface including at least one of aprotrusion, a ratchet, a spike, a spline, surface roughenings, andknurling.
 46. The implant of claim 30, wherein said implant includes atleast two members, each member having a leading portion, a trailingportion, a top, a bottom, and at least one side, each member beingadapted to be placed side by side with another of said members, saidleading portion of said members forming said leading end of said implantwhen placed side by side.
 47. The implant of claim 46, wherein saidimplant includes two of said members, each member being a mirror imageof the other.
 48. The implant of claim 46, wherein each member includesat least a portion of said at least one opening.
 49. The implant ofclaim 30, in combination with a bone growth promoting material.
 50. Theimplant of claim 49, wherein said bone growth promoting material isselected from one of bone, bone derived products, demineralized bonematrix, mineralizing proteins, ossifying proteins, bone morphogeneticprotein, hydroxyapatite, and genes coding for the production of bone.51. The implant of claim 30, wherein said implant is treated with a bonegrowth promoting substance.
 52. The implant of claim 30, wherein saidimplant is at least in part resorbable.
 53. The implant of claim 30, incombination with a chemical substance adapted to inhibit scar formation.54. The implant of claim 30, in combination with an antimicrobialmaterial.
 55. The implant of claim 30, wherein at least a portion ofsaid implant is treated to promote bone in growth between said implantand said adjacent vertebral bodies.
 56. The implant of claim 30, incombination with at least one spinal fixation implant.
 57. The implantof claim 39, further comprising a curved transition between at least oneof said opposite sides and said trailing end, said curved transitionforming at least part of an arc of a circle.
 58. The implant of claim30, wherein said trailing end is adapted to receive at least one bonescrew adapted to engage at least one vertebral body when insertedthrough said implant.
 59. The implant of claim 58, further comprising alock for locking at least one bone screw to said implant.